Method of making aminophenol derivatives



Patented Feb. 4, 1 930 No Drawing.

UNITED STATES PATENT OFFICE HANS T. CLARKE, OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COM- ROCHESTER, NEW YORK, A. CORPORATION OF NEW YORK METHOD OF MAKING AMINOPHENOL DERIVATIVES Application filed April 3,

This invention relates to an' improved method for the preparation of'monoalkyl derivatives of o-aminophenol. The monomethyl derivative is of particular importance, as its sulfate is a well known photographic developing agent.

The regular methods of methylation when I a applied too-aminophenol yield as the principal product the dimethyl compound, unless a very large excess of the original aminophenol be present. The latter condition naturally involves disadvantageously large amounts of.

labor and losses of product.

I have found that the o-aminophenol may be so treated with a carboxylic acid as to yield the corresponding benzoxazole, and this compound forms with an alkyl halide orother alkyl ester of the inorganic type an addition prodnot which on treatment with dilute acids or alkalies is practically quantitatively converted into. the acyl derivative of the required monoalkyl aminophenol; this acyl compound can then be readily hydrolyzed andthe required salt prepared in the usual way, the carbox, lic acid being regenerated. It will be seen t at in this process the acid plays a cyclic role.

' fully described.

The steps of the Step (a) .A convenient method of effecting the first step is to'h v temperature between 175 to 190 0., the o-aminophe'nol with a slight excess of acetic acid withthe use of'a fractionating column until no more water distills over, yielding the known compound l-methyl-benzoxazole.

v The reactions involved in this step are thefollowing:

warmed to 80-100" C.' with an equimolar process will novv beunore- 1924. serial No. 704,072.

quantity of methyl sulfate. The resulting ad dition compound separates in the form 0 colorless needles. It has been found advantage" ous, though not necessary, to dilute the origi-v nal oxazole with an indifferent solvent of sufficiently high boiling point, such as toluene, from which the salt separates and may thus be obtained, by decantation of the solvent, free of unchanged reagents. The degree of dilution may be varied within extremely wide limits. As the salt is'in a moltenstate at the reaction temperature, the reaction mixture must, of course, first be allowed to cool.

The reaction involved in step (b) is the following:

ONa

Nomoocm HCl=CtH Step (d) .The acetyl-methyl-aminophe- [101 is then hydrolyzed by boiling with an excess of dilute sulfuric acid, then freed from such excess acid by means of calcium carbonate or similar material producing an insoluble sulfate and the resulting solution cooled when o-methyl aminophenol sulfate separates in crystalline form and the original carboxylic acid is regenerated.

. 25 fiy April, 1924.

The reaction involved in step (d) is represented by the following equations:

ms o.+2omoo,H. Ncmooom QH CoH4 NHOH: 2

5 Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

The herein described process comprising 0 the treatment of o-aminophenol with acetic acid at a temperature between 175 and 190 C. until l-methyl-benzoxazole is produced, the

treatment of the l-methyl-benzoxazole with methyl sulfate at a temperature between 80 and 100 C., until an addition compound is 1 produced; the treatment of the addition compound with an alkali and then with an acid until acetyl-methyl-aminophenol is produced,

then boiling this last compound with sulphuric acid to form o-methyl-aminophenol sulfate and to regenerate acetic acid and utilizing the regenerated acetic acid to continue the process.

' Signed at Rochester, New York, this 1st HANS T. CLARKE. 

